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 A342957 a(n) is the least k such that A342956(k) = n. 1
 1, 2, 4, 15, 39, 87, 183, 951, 1255, 1527, 3063, 15335, 12279, 61431, 49143, 516047, 491495, 1703767, 1310695, 8257487, 3145719, 15728631, 12582903, 94371815, 50331639, 352321527, 335544295 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) exists for all n, as A342956(2^(2^k)) = k+1. If 2^n = p+q where p and q are primes, then A342956(p*q) = n so a(n) <= p*q <= 2^(2*n-2). Goldbach's conjecture implies such p and q exist for all n >= 2. LINKS Table of n, a(n) for n=0..26. EXAMPLE a(3) = 15 because A342956(15) = 3 and this is the first appearance of the value 3 in A342956. MAPLE f:= proc(n) local t; numtheory:-bigomega(add(t[1]*t[2], t=ifactors(n)[2])) end proc: V:= Array(0..18): count:= 0: for n from 0 while count < 19 do v:= f(n): if v <= 19 and V[v] = 0 then count:= count+1; V[v]:= n fi od: convert(V, list); MATHEMATICA Table[n=0; While[PrimeOmega[Plus@@Times@@@FactorInteger@++n]!=k]; n, {k, 0, 14}] (* Giorgos Kalogeropoulos, Aug 20 2021 *) CROSSREFS Cf. A342956. Sequence in context: A153945 A153942 A055466 * A148267 A148268 A148269 Adjacent sequences: A342954 A342955 A342956 * A342958 A342959 A342960 KEYWORD nonn,more AUTHOR J. M. Bergot and Robert Israel, Mar 30 2021 EXTENSIONS a(25)-a(26) from Chai Wah Wu, Mar 31 2021 STATUS approved

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Last modified December 9 07:10 EST 2023. Contains 367689 sequences. (Running on oeis4.)